Air pollution control process

ABSTRACT

An air pollution control process employing an improved rotatable collector, which by its position becomes a filtering and adsorbing station and a combustion and desorbing station, and an oxidizer are utilized in an apparatus and process for removing airborne particulate materials and organic vapors from an air stream. The rotatable collector comprises an assembly of alternate layers of refractory microfiber, metal screens, and a thin layer of adsorbent carbon.

This is a division of application Ser. No. 190,196 filed Sept. 24, 1980,now U.S. Pat. No. 4,348,362.

FIELD OF THE INVENTION

This invention relates to the removal of pollutants in gas streams andmore particularly to apparatus and a method for the removal of organicvapors and airborne particulate matter from an air or gas stream.

BACKGROUND ART

The removal of obnoxious, odorous materials from gas streams, whetherthey are in industrial, commercial, or domestic environments, is aproblem that is rapidly becoming more serious each year. Environmentalcontrol agencies are instigating increasingly stringent regulations tocontrol objectionable emissions of all types, and at the same time anation-wide energy crisis demands a reduction in the use of fuels forthis purpose. Processes for the removal of pollutants from a gas streamutilizing incineration, adsorption, impingement, electrostaticattraction, centrifugation, sonic agglomeration, and ozonization areknown. The most common of these processes in use at present appears tobe incineration by direct flame or catalytic oxidation. Although theseprocesses will remove particulates and organic vapors from a gas stream,they do so only with the expenditure of large amounts of energy and/oradsorbent material. Such processes may be non-continuous and thereforerequire interruption of the process, or they may employ oxidationcatalysts subject to poisoning, and therefore are not entirelysafisfactory.

U.S. Pat. No. 3,658,724 discloses an adsorbent catalyst for use in theremoval of odorous and combustible components from the effluent gases ofcooking and other processes by passing the effluent gases through a bedof the adsorbent catalyst and continuously or cyclicly oxidizing (byusing a metallic oxidation catalyst known in the art which isincorporated in the adsorbent catalyst) the adsorbed components byincreasing the temperature up to 300° C.

U.S. Pat. No. 3,908,367 discloses a process for cleaning exhaust fumesfrom a combustion device by causing them to flow through a moving filterthat is continually cleaned by air flowing through the filter in thedirection opposite to the flow of exhaust fumes therethrough, and thenceinto the combustion device for reburning certain fume products capturedby the filter. The filter useful in such a process captures mainlyunburned carbon and metal particles and will not adsorb an appreciableamount of vapors, and even if it did adsorb vapors, there is no step ofthe process which would allow for desorption of the vapors so that thesevapors could be subjected to reburning in the combustion device.

U.S. Pat. No. 3,930,803 discloses apparatus for purifying a gas streamof combustible vapors by passing the stream through an adsorption filterand charging the filter with combustible impurities to a predeterminedlevel whereon, in a cyclic operation, the stream is interrupted and thefilter is desorbed by passing a heated inert gas generated bystoichiometric burning of hydrocarbons through the filter, or the gasflow is switched from a saturated to a regenerated adsorption filter.The inert gas enriched with desorbate flows to a second burning chamberwhere air is added and the desorbate burned. Such a process is notcontinuous and does not provide for the removal and disposal ofcombustible particulate material in a gas stream.

Assignee's copending patent application, U.S. patent application Ser.No. 21,997, filed Mar. 19, of 1979 and now abandoned in the names of C.Davis, G. Foss, and T. Shevlin, discloses a system for the removal ofparticulate material from an air stream in a continuous,energy-efficient process. The improved collector of the presentinvention provides for the removal of organic vapors as well asparticulate matter from a gas stream and affords the removal of at least85%, and preferably at least 95%, of the total organic content of an airstream.

The superior energy efficiency of the collector of the present inventionresults from the use of much thinner adsorbent beds than is used inprior art apparatus. These thinner beds require much less energy fortheir regeneration. In addition, the concentration of organic vaporsrealized by use of the collector of the present invention makes possiblea reduced energy requirement for the processing of this concentratedstream.

SUMMARY OF THE INVENTION

The present invention provides a process and apparatus for continuouslyremoving airborne particulate material and organic vapors from apolluted air stream, the process comprising the steps of:

(1) collecting from an air stream, by filtration and adsorption,particulate material and organic vapors, thus forming an essentiallypollutant-free effluent,

(2) burning the collected particulate matter and simultaneouslydesorbing the collected organic vapors, thus forming a concentratedstream comprising combustion products of particulate material anddesorbed vapors,

(3) oxidizing the desorbed vapors of the concentrated stream to form anessentially pollution-free oxidized stream comprising both particulatematerial combustion products and vapor combustion products, and

(4) exhausting, separately, the essentially pollutant-free effluent ofstep (1) and the essentially pollutant-free oxidized stream of step (3);

said process taking place in an apparatus comprising:

(1) a housing having an inlet plenum for introduction of a polluted airstream thereinto,

(2) a rotatable collector located within said housing, said collector,by its position being

(a) a filtering and adsorption station for particulate matter andorganic vapors, and having connecting means therefrom to an outletplenum for exhausting the resultant pollutant-free air stream, and

(b) a combustion and desorption station for combustion of particulatematter and desorption of organic vapors,

(3) oxidizing means for converting the desorbed vapor into oxidizedpollutant- free products,

(4) connecting means for providing passage for the resultant combustionproducts and desorbed vapors from the combustion and desorbing stationto the oxidizing means,

(5) connecting means for providing passage for the combustion andoxidized products from the oxidizing means to the atmosphere or,optionally, back to the inlet plenum, and

(6) means for moving the rotatable collector continuously from thefiltering and absorbing station to the combustion and desorbing station.

The term "pollutant-free" as used herein is defined in accordance withthe definition given by Rule 442 of the State of California South CoastAir Quality Management District Rules and Regulations adopted May 7,1976 and amended July 6, 1979. This definition states: "Pollution-free"is the term applied to the treated effluent from a source emitting anair stream having a carbonaceous content that has had its totalcarbonaceous content reduced either 90% by thermal oxidation to carbondioxide and water or 85% by adsorption. This rule is generally acceptedby the trade as being the most stringent set forth to date.

The present invention, utilizing an improved collector, provides amethod and means of air pollution control that is superior to those ofthe prior art. Herein is provided an energy- and adsorbentmaterial-efficient method for continuous removal of both airborneparticulate material and organic vapors from an air stream, by whichmethod the total organic content of an air stream is reduced by at least85%, and preferably by 95% or more. The present invention provides acollector for both airborne particulate material and organic vapors fromwhich the combustible particulate material can be burned and the organicvapors desorbed without destroying the adsorbent material, a surprisingfeature in the view of the known flammability of activated carbon. Thecollector, of laminar construction, comprises an assembly of at leastone layer, and up to four layers, each of adsorbent beds, metal screens,and refractory microfiber mats.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawing,

FIG. 1 is a transverse sectional view of a preferred apparatusillustrating one embodiment of the invention;

FIG. 2 is an enlarged portion of one embodiment of the movable collectorof use in the apparatus of the invention;

FIG. 3 is an enlarged portion of another embodiment of the movablecollector of use in the apparatus of the invention; and

FIG. 4 is a transverse sectional view of another embodiment of theapparatus of the invention.

DETAILED DESCRIPTION

The process and apparatus of the invention will be more fully understoodfrom the following description taken in conjunction with theaccompanying figures. Reference numbers refer to similar partsthroughout the several views of the figures.

Referring to FIG. 1, there is shown a preferred embodiment 10 of theapparatus of the invention for the simultaneous removal of vaporous andcombustible particulate pollutants from gas streams comprising housing12, an inlet plenum 14 for conducting polluted gas streams 16 comprisingvaporous and particulate materials into the housing 12, and outletplenum 18 for conducting cleaned gas from the housing. Polluted gas 16can be forced optionally from a source of pollution by blowers not shownor, preferably, pulled into inlet plenum 14 by blower 46 in exit plenum18. The polluted gas 16 passes into the apparatus 10, fills housing 12,and is forced through rotatable collector 22 that is secured to theperiphery of metal drum 24, which has perforations 26 in its cylindricalsurface, into the drum interior 28. In passing through the movablecollector 22, particulates and organic vapors in the polluted gas aredeposited on and adsorbed by collector 22. Metal drum 24 is axiallymounted for rotation within housing 12 on journals 29 and 30 that turnin bearings 32 and 34 respectively that are located in opposite walls 36and 38 of housing 12. Journal 30 extends through bearing 34 in wall 38and is driven rotationally by means 39, such as the belt driven sheave40 shown. Journal 29 that turns in bearing 32 located in wall 36 is ametal tube of sufficient internal diameter to permit egress of cleanedgas 20 without appreciable pressure buildup within the housing intooutlet plenum 18. Linear tube burner 44 is located within housing 12 sothat flame 42 from burner 44 impinges across the width of movablecollector 22. Within drum interior 28 is housing 48 having a funnel-likeconfiguration with an open base 50 located in close proximity to theinner surface of drum 24 and directly across movable collector 22 fromlinear burner 44. Open base 50 has dimensions of length and width suchthat the area of collector 22 heated by flame 42 is essentiallycompletely covered so that combustion products and desorbed vapors 52released from collector 22 upon heating by flame 42 enter housinginterior 54 and are pulled to oxidizer 58 by a blower, not shown,through pipe 56 or by venturi 60 in inlet plenum 14. Oxidized vapors 62exiting oxidizer 58 are essentially pollutant-free and can be vented(not shown) to the atmosphere or optionally recycled to inlet plenum 14.

During operation, drum 24 is rotated, presenting successive portions ofcollector 22 first to incoming polluted air at a filtering and adsoringstation located across inlet plenum 14 for the removal of particulatematerial and vapors by filtration and adsorption by collector 22, andsecond, at a combustion and desorbing station, to heat at a temperatureof at least 600° C. on the exposed surface of collector 22 and about200° C. to 450° C. at the vapor adsorber layer (described below) ofcollector 22. Under these temperature conditions the particulatematerial deposited onto the surface of collector 22 is burned and thevapors desorbed. The products of combustion of the particulate materialand the desorbed vapors 52 pass into housing 48 and are conducted bypipe 56 to oxidizer 58 where they are completely oxidized. In thismanner, the volume of vapors 52 is only about 10 to 20% of the totalvolume of polluted air 16 entering housing 12. By this concentration ofvapors the energy requirement for burning of vapors is greatly reduced.

In the embodiment shown in FIG. 1, heat is supplied by flames 42provided by the combustion of fuel issuing from linear tube burner 44(e.g., Slot Burner, available form Selas Corporation of America,Dresler, Pa. 19025) in close proximity to the surface of collector 22.Optionally, heat can be supplied by an electrical resistance element ora focused infrared tubular quartz lamp having an elliptical reflectorelement. In accordance with the invention, drum 24 is rotated at a speedsuch that the temperature of the exposed surface of collector 22 havingdeposited particulate material thereon is raised at the combustion anddesorbing station to about 600° C. in less than about 0.4 seconds andthe vapor adsorber layer 84 in FIG. 2 (described below) is raised to atemperature between 200° and about 450° C., preferably 200° to about400° C., in about the same time. Preferably the adsorbent material ofthe vapor adsorber layer has an air ignition temperature greater than400° C.

The combustion and adsorbing station should be capable of heating thesurface of a refractory material having a density between 4 and 40 mgper cubic centimeter and a coefficient of thermal conductivity of lessthan 5×10⁻² g-cal/sec (cm²) (°C./cm) to a temperature of at least 600°C. in less than about 0.4 seconds and preferably in less than about 0.1second.

Generally, rotational speeds such that the surface speed of collector 22is between 0.1 and 10 cm/sec allow for the attainment of thesetemperatures. At surface speeds greater than about 10 cm/sec,temperatures attained on the collector are reduced resulting inincomplete combustion and desorption from collector 22. At surfacespeeds of less than about 0.1 cm/sec, the temperature of the vaporadsorber layer 84 of collector 22 may reach above about 450° C. andbring about the combustion of the adsorber material when the adsorbermaterial is activated carbon.

Movable collector 22 comprises laminar constructions of one or moremetal screens, mats of refractory microfibers, and beds of gas adsorbentmaterials having a pressure drop across the laminae of less than about300 mm, and preferably less than about 25 mm, of water. Generally, thecollector has a total thickness of less than about 50 mm, preferablyless than about 25 mm, and most preferably from about 10 mm to 15 mm, ofwhich the gas adsorbent bed or layer has a thickness of about 1 to 20mm, preferably 2 to 10 mm. It is unique with this invention to use suchthin adsorbent beds. Thin adsorbent beds require much less energy fortheir regeneration, thereby resulting in economy to the user. Inaddition, the initial cost of a thin adsorbent bed is much less thanwhere thick adsorbent beds are used. Although any solid gas adsorbentcan be used, for example, alumina, silica gel, molecular sieves,adsorbent-impregnated refractory microfiber, or activated earths; thepreferred solid adsorbent is activated carbon. Activated carbon havingparticle size of about 140 mesh is preferred; however, particle sizesfrom about 20 to 200 mesh can be used.

The enlarged portion of one embodiment of movable collector 22 isillustrated in FIG. 2 in which there is provided a laminar constructionof metal screens 80, mats of refractory microfibers 82, and gasadsorbent bed 84 (which consists of a layer of adsorbent material 90between mats of refractive microfibers 88) and metal screens. Arrow 86shows the direction of gas flow when collector 22 is over burner 44 inthe operation of apparatus 10. The movable collector 22 of FIG. 1 has acylindrical shape.

FIG. 3 shows an enlarged portion of another embodiment of movablecollector 22 in which gas adsorbent bed 84 comprises adsorbent material90 loaded into refractory microfibers 88. The movable collector 22 ofFIG. 3 has a cylindrical shape.

FIGS. 2 and 3 show movable collectors consisting of laminar constructionhaving at least one gas adsorbent bed and several each of alternatingmetal screens and microfiber mats. Laminates of alternating layers ofone to four of each of gas adsorbent beds, microfiber mats, and metalscreens can be used provided that the overall construction has athickness of no more than about 25 mm and a pressure drop of no morethan 300 mm of water.

Metal screen 80 can be of any metal, but preferably is stainless steelhaving mesh size from about 20 to about 60. If the screen mesh issmaller than about 60, an undesirable pressure drop is caused, and itdoes not have the mass for a good heat sink. If screen mesh is largerthan about 20, heat does not dissipate sufficiently fast from thecollector to allow for adsorption of gases in the adsorption stage ofthe operation. By optimizing the mesh size and the carbon bed thicknessit is possible to achieve a temperature in the carbon bed that is highenough to desorb the organic vapors but not so high as to causecombustion of the activated carbon.

As described above, gas adsorption bed 84 can be a layer of adsorbentmaterial 90, preferably activated carbon, between layers of refractorymicrofibers 88 or it can be a layer of refractory or hightemperature-resistant glass microfiber having impregnated thereinadsorbent materials, preferably activated carbon. Bed 84 can also be anadsorbent material impregnated ceramic honeycomb. (Ceramic honeycombstructures are disclosed in U.S. Pat. No. Re. 27,747). A particularlydesirable bed comprises a laminar construction of a sheet of expandedmetal between layers of refractory microfibers in which the intersticesof the expanded sheet are filled with activated carbon. An example of asuitable commercially available gas absorption bed is "CRANEMAT", afiltration medium from Crane & Co., Inc., Dalton, Mass. 01226, whichconsists of a non-woven glass matrix containing about 20 percent byweight of activated carbon.

Preferred refractory microfiber mats 82 and layers 88 for use in movablecollector 22 are prepared from fibers described in U.S. Pat. Nos.3,713,865, 3,770,487, 3,793,041, 3,795,524, 3,853,567, 3,892,583 and4,047,965. The microfibers described in U.S. Pat. No. 3,793,041 comprisea mixture of microcrystalline zirconia and amorphous silica in a moleratio of 1.5:1 to 1:2, have diameters in the range of 10 to 40 μm anddensities in the range of 1.5 to 4.3 g/cc. The microfibers described inU.S. Pat. No. 3,795,524 are aluminum borate or aluminum borosilicatehaving a mole ratio of alumina:boria of 9:2 to 3:1.5, have diameters of10 to 15 μm or more. The microfibers described in U.S. Pat. No.4,047,965 have mole ratios of alumina to silica that range from 3Al₂O₃.1.75SiO₂ to 3Al₂ O₃.2.19SiO₂ (this corresponds to 67 to 77 weightpercent alumina to 23 to 33 weight percent silica). Other suitablecollector mats are prepared from refractory fibers such as the aluminafibers described in U.S. Pat. Nos. 3,950,478 and 3,982,955.

The term "refractory microfiber", as it is used in the presentinvention, is defined as a non-metallic, inorganic, amorphous,microcrystalline material or a mixture of amorphous and microcrystallinematerials that are either vitreous or non-vitreous, are stable (i.e., dono melt or decompose) at temperatures of at least 600° C. (preferably atleast 800° C.), preferably have a coefficient of thermal conductivity ofless than 0.02 cal/(sec)(cm²) (°C./cm) at 20° C., have an averagediameter of about 0.1 to 20 μm and a length to diameter ratio of atleast 1000. The composition of said refractory microfiber can benarrowly defined by the formulae

    M.sup.1 X.sub.a.M.sup.2 X.sub.b.M.sup.3 X.sub.c . . . M.sup.n X.sub.z

wherein

M¹, M², M³, . . . M^(n) individually represent elements exclusive ofperiodic groups 6A, 7A and 8 of the Periodic Chart of Elements andhydrogen,

n is the number of different elements present in the compositionexclusive of hydrogen and Groups 6A, 7A and 8,

X is preferably oxygen, but also includes nitrogen, carbon, or boron,

(a,b,c, . . . z) are numbers (not necessarily whole integers) or zerowhich represent the empirical proportions of the different elementalcompounds that they prefix, and at least one of a,b,c, . . . z may berepresented as one, and a,b,c, . . . z individually represent the numberof atoms of X for each atom of M¹, M², M³, . . . M^(n), respectively.

Examples of commercially available suitable refractory microfibersinclude Kaowool 2300® and Kaowool 2600®, alumina-silica fibers having47% and 55% alumina respectively (available from Babcock and Wilcox);Saffil®, a 95% alumina-silica fiber (available from Imperial ChemicalIndustries); boron-nitride fibers (available from Carborundum Co.); andzirconia fibers (available from Zircar Products Inc.).

Representative elements which are preferred as M¹, M², M³, . . . M^(n)include, but are not limited to silicon, aluminum, magnesium, boron,zirconium, calcium, chromium, hafnium, tantalum, tungsten, molybdenum,titanium, vanadium, lead, zinc iron, nickel, tin, copper and silver.Less preferred materials specifically include lithium, potassium,sodium, mercury, platinum and gold. The transuranic and translanthanideelements would also be less preferred.

The size and nature of the microfibers as described above are criticalboth for the ability of the filtering mass to catch volatileparticulates and to hold the particulates when they are being combusted.Smaller fibers will merely hold the matter on the mat surface as if themat were a flat surface, and larger fibers would not catch a largeproportion of the particulates.

The collector mats 82 can have a thickness of from about 2.5 to 25 mm,preferably about 5 to 15 mm, the lower limits utilizing fibers of about1 μm to less than about 20 μm in diameter and the upper limits utilizingfibers having diameters up to about 40 μm. Preferably, the fibers have adiameter of from about 1 to 5 μm. Bulk densities of the collector fibermats can be between about 4 and 40 mg/cc and preferably between about 10and 25 mg/cc. Collector mats having a thickness below about 2.5 mmdecrease in effectiveness for stopping particulate material withdecreasing thickness and collector mats having a thickness greater thanabout 25 mm have increased pressure drop across the collector without acorresponding increase in particulate stopping efficiency. Aparticularly desirable collector has an intermediate layer of coarserefractory microfibers (e.g., 10-100 μm diameter) of 10 to 15 μmthickness separating the collector mat 22 of fine microfibers (e.g., 5to 15 μm diameter) of 5 to 10 mm thickness from the collector support24. Means for removing uncombustible particulates collected on collector22 at a position after the heat source by use of small tapping hammersis also contemplated.

FIG. 4 shows another embodiment 70 of the apparatus of the inventionwherein the movable collector 22 is secured to metal disc 25 havingperforation 26 in its surface. In operation, disc 25 is rotated by means41 presenting successive portions of the surface of movable collector 22to polluted gas 16 then to heat means 42. Within interior 28 of housing12 is housing 48 having open base 50 located in close proximity to thesurface of movable collector 22 and directly across movable collector 22from burner 44. Desorbed vapors and combustion products 52 released fromcollector 22 enter housing interior 54 and are pulled to vapor oxidizer58 through pipe 56. Vapors 52 are oxidized in an oxidizer 58 from whichoxidized vapors 62 exit and can be vented to the atmosphere oroptionally recycled (not shown) to inlet plenum 14. Other parts of theapparatus of this embodiment have functions similar to those describedfor the embodiment of FIG. 1.

Vapor oxidizer 58 is preferably a catalytic oxidizer such as a "TORVEX"catalytic reactor manufactured by E. I. DuPont De Nemours and Company ofWilmington, De. Another useful vapor oxidizer 58 is a catalytic vaporoxidizer such as the "Honeycat®" vent gas purifier manufactured by W. J.Inc. of Cleveland, Ohio. Other oxidizers that may be used include thevarious thermal or direct firing oxidizers which are well known in theart of pollution control. Still another means contemplated for use asvapor oxidizer 58 for organic vapors 52 is an ozonizer such as the "KTFume Scrubber" Ozonator manufactured by Plastics Constructions, Ltd. ofLondon, England, and described in "Process Engineering", p. 77 (Nov.1974). In such a device, the desorbed vapors 52 are contacted with ozonefor a sufficient time to oxidize substantially all of the desorbedvapors. Effluent 62, from the ozonizer is, preferably, returned toapparatus 70 via plenum 14 where unreacted ozone is decomposed andunoxidized organic substances are recycled.

Objects and advantages of this invention are further illustrated by thefollowing example, but the particular materials and amounts thereofrecited in this example, as well as other conditions and details, shouldnot be construed to unduly limit this invention.

EXAMPLE

An apparatus in accordance with FIG. 1 was constructed to have movablecollector 22 secured to the periphery of a drum of 1.6 mm (1/16 inch)stainless steel 30 cm in diameter and 13.5 cm long. The cylindricalsurface was perforated with holes having a 3 mm diameter and spaced in ahexagonal array on centers 8 mm apart. Effective collector area could beadjusted by blocking off the perforations of the drum with strips ofmetal backed adhesive tapes placed about the drum to leave a desiredcollector area. Collector 22 could also be varied by placement ofvarious materials as a belt over the exposed perforations. Inlet plenum14 had a cross-sectional area of 0.018 m². Blower 46 was of conventionaldesign and in the absence of collector 22 provided an exhaust volume of9.3 m³ per minute. The exhaust volume could be varied by use of a damper(not shown) in the outlet plenum. Flow rates were measured by use of an"Alnor" thermoanemometer (available from the Alnor Instrument Company ofChicago) placed in the intake plenum 14. The combustible particulatecontaining gas stream was an aerosol containing 1270 mg/min of solidsgenerated by atomizing a 10% solution in toluene of an Amberol® M-82(Rohm & Haas) phenolic resin at a pressure of 2.1 kg/cm² aboveatmosphere using an aerosol generator such as is described by Whitby etal, International Journal of Air and Water Pollution, 9, 263-277 (1965).The mean particle diameter of the aerosol at the point of entry toplenum 14 was 0.3 micrometers with none larger than 2 micrometers asdetermined by transmission electron microscopy.

The aerosol consisting of Amberol® M-82 particulate matter was monitoredat various locations in the apparatus by means of an Active ScatteringAerosol Spectrometer® ASAS-300A (Particle Measuring Systems, Inc., 1855South 57th Court, Boulder, Colo. 80301). The toluene vapor concentrationin the gas stream was monitored using hnu® Photoionizer Model PI-101(hnu Systems, Inc. 383 Elliot St., Newton Upper Falls, Ma. 02164) whosesignal was read continuously off a Hewlett-Packard® 7100B strip chartrecorder. Various rates of speed of the collector could be obtained byvarying the voltage to the motor driven sheave 40. Heat source 44 was anatural gas fueled ribbon burner.

A movable collector was prepared by placing a refractory microfiber mat(10 mc wide×80 cm long) in the botton of a 100 cm×30 cm containercontaining water at a depth of about 25 mm. A slurry of 100 g of 140mesh activated carbon, WITCARB® AC7965 (from Witco Carbon Co., 277 ParkAvenue, New York, NY 10017) was uniformly and slowly poured into thecontainers. After allowing the mixture to settle for about 30 minutes,the water was drained from the container leaving a layer of carbondeposited on the refractory microfiber mat. While the carbon was stillwet, a second refractory microfiber mat was placed on top of the carbonlayer to form a sandwich. This sandwich was then removed from thecontainer and mounted onto the collector drum of the apparatus andsecured in place with ceramic thread. The sandwich was allowed to dry.There was then fastened onto the sandwich alternately three each of 25mesh stainless steel screen and refractory microfiber mat. The resultingcollector had an overall thickness of about 10 mm of which the activatedcarbon layer was 2 mm.

A platinized ceramic honeycomb catalyst element (as disclosed in U.S.Pat. No. 4,206,083, EXAMPLE 1) was introduced into pipe 56 along with a2000 watt electric heating element used to bring the air streamtemperature up to about 400° C. which was the oxidizing temperature ofthe catalyst element while a gas flow of 0.14 m³ /min was passingthrough it, while the total air flow through the apparatus was 0.77 m³/min. The results are shown in TABLE I where the reduction inparticulate (on a mass basis) is better than 99% and the reduction intoluene concentration is better than 89%, indicating a total reductionin carbonaceous matter of 98%.

                  TABLE I                                                         ______________________________________                                        Particulate (Counts)                                                                        Range      Range                                                              0.2-0.6    0.2-3.0 Toluene                                      Sample        micron     micron  (ppm)                                        ______________________________________                                        Upstream 16   15301      2595    458                                          Downstream 20 416        23      51.5                                         Secondary exhaust                                                                           9205       0       1004                                         before catalyst 52                                                            Secondary exhaust                                                                           280        0       0.4                                          after catalyst 62                                                             ______________________________________                                    

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

What is claimed is:
 1. A process for removing volatile particulatematerial and organic vapors from a polluted air stream, said processcomprising the steps of:a. providing said polluted air stream forentrance into an inlet plenum of an apparatus housing, said apparatushousing having a rotatable collector and burner located therein, saidrotatable collector by its position being(1) a filtering and adsorptionstation for particulate matter and organic vapors, and having connectingmeans therefrom to an outlet plenum for exhausting the resultantpollutant-free air stream, and (2) a combustion and desorption stationfor combustion of particulate matter and desorption of organic vapors,b. collecting particulate material and organic vapors from said airstream at said filtration and absorption station in said collector toform an essentially pollutant-free effluent, said collector comprisingan assembly of layers of refractory microfiber mats, metal screens, andvapor adsorbents, one of said refractory microfiber mats being on theexposed surface of said collector adjacent to said burner and beingcapable of withstanding temperatures of at least 600° C. produced bysaid burner, the microfibers having diameters in the range of 0.1 to 40m and said microfiber mats having a thickness in the range of 2.5 to 25mm and a bulk density in the range of 4 to 40 mg/cc, and one of saidvapor adsorbent layers which is capable of withstanding temperatures upto 450° C. being on the inner surface of said collector, said collectorhaving a pressure drop of less than 300 mm of water, c. burning saidcollected particulate matter and simultaneously desorbing said collectedorganic vapors, at said combustion and desorption station in saidcollector, to form a concentrated stream comprising combustion productsof particulate material and desorbed vapors, d. oxidizing the desorbedvapors of the concentrated stream in an oxidizing means in saidapparatus to form an essentially pollution-free oxidized streamcomprising both particulate material combustion products and vaporcombustion products, and e. exhausting, separately, the essentiallypollutant-free effluent of step b. and the essentially pollutant-freeoxidized stream of step d.
 2. The process according to claim 1 whereinthe concentrated stream of step (c) comprises up to about 20% of thetotal volume of the entering air stream of step (a).